Wind Induced Hanger Vibrations – the Hålogaland Suspension Bridge

The hangers of the Hålogaland suspension bridge were recognised to vibrate during the final stages of construction, vibrations that persisted after the opening of the bridge to traffic. A preliminary survey indicated that the vibrations were due to vortex shedding excitation and thus could be mitigated by the addition of mechanical damper elements. The present paper gives an account of a measurement exercise launched to clarify the cause of the vibrations and to guide the placement of Stockbridge dampers on the individual hangers. Analysis of the measurements indicated that the structural damping of the hanger cables was significantly less than proposed by current engineering codes of practice and that vortex induced vibrations of the hangers occurred in a much wider wind speed range than proposed by guidelines in the field of electrical overhead conductors.